1. Technical Field
The invention relates to a method of influencing the contact angle of the planar surface of an object, in particular the nozzle surface of an inkjet printhead, in which method the nozzle surface of the printhead is provided with a polymer layer.
2. Background Art
DE-A-42 10 160 discloses a method and apparatus for applying a hydrophobizing agent, said method preventing penetration of the hydrophobizing agent into the openings to be kept free. A coating tool consisting of a resilient member having a capillary system is moved across the surface of the object to be treated. A leading contact surface of the resilient member thereby seals the openings. Downstream of the contact surface, the dissolved hydrophobizing agent is applied to the part to be treated in that it is supplied to its surface via the capillary system of the resilient member. The ink channels are additionally subjected to an inert gas atmosphere in order to prevent the hydrophobizing agent from contacting said channels.
WO 90/14958 proposes a hydrophobizing agent and a different method of application, in particular for inkjet printheads. As an effective component, the hydrophobizing agent comprises a silane, an at least partially fluorinized organic group thereof being bonded to the silicon by means of a saturated residue. In a vacuum chamber, the hydrophobizing agent is vapor-deposited on an inkjet printhead. For this reason, a certain amount, of the hydrophobizing agent is evaporated and deposited on the nozzle surface of the inkjet printhead. Penetration of the hydrophobizing agent into the ink channels is prevented by flowing an inert gas therethrough. The inkjet printhead thus provided with the vapor-deposit is then subjected to a temperature treatment in which individual molecules of the hydrophobizing agent are bonded to and partly cross-linked with the materials of the inkjet printhead surface.
In the two above-mentioned methods of hydrophobizing additional measures such as flushing the ink channels with inert gas, filling the channels with mercury etc., have to be taken so as to prevent the ink channels from being penetrated by the hydrophobizing agent. This is extremely important as the ink channels are hydrophilic by nature in order that the flow of the water-based ink is facilitated. Areas or islands in the interior of the ink channels having hydrophobic properties would adversely affect the ink supply rate to the nozzle ports. Moreover, adhesion of the hydrophobizing layers may suffer under the action of ink.